1. Field of the Invention (Technical Field)
The present invention relates to a medical apparatus and process to treat and assist bone and tissue repair and regeneration.
2. Description of Related Art
Stress-induced microcurrents in the development and maintenance of bone strength and healing in both tissue and bone, following fractures or other trauma, can aid conventional modalities in the treatment of persistent infections, burns, and a variety of other conditions including bone repair.
The application of electrical energy to injured tissues has been an acceptable mode of medical therapy for many years and is well characterized. Application of electrical stimulation can promote wound healing and low intensity direct current stimulation can be switched between negative and positive polarities during the course of treatment. Traditional microcurrent electrotherapy treatment produces a series of microcurrent waveform signals that are directed to a selected treatment area of a human or animal. Historically electrotherapy methods primarily utilized only a single waveform and/or current setting for the duration of the treatment but more recently multiple forms have become common.
The following are examples of such implanted systems that deliver electrical pulses to repair tissue. Note that the following discussion refers to a number of publications by author(s) and year of publication, and that due to recent publication dates certain publications are not to be considered as prior art vis-a-vis the present invention. Discussion of such publications herein is given for more complete background and is not to be construed as an admission that such publications are prior art for patentability determination purposes.
U.S. Pat. No. 4,982,742 to Claude, entitled “Apparatus and Method to Facilitate Healing of Soft Tissue Wounds”, issued Jan. 8, 1991, discloses a method for applying therapeutic microcurrent excursions and a bandage containing circuitry for generating microcurrent excursions comprising an assemblage with two electrodes and a power supply. U.S. Pat. No. 4,556,051 to Maurer, entitled “Method and Apparatus for Healing Tissue,” issued Dec. 3, 1985, discloses a method for promoting healing with interacting electric current and a magnetic flux field and electrodes adhesively attached to skin adjacent the injured tissue, and discloses a variation of an externally applied two electrode electrostimulator device in combination with an apparatus to simultaneously produce magnetic field pulses. U.S. Pat. No. 6,607,500 to Da Silva et al., entitled “Integrated Cast and Muscle Stimulation System,” issued Aug. 19, 2003, disclose a device that allows electrical stimulation, in the form of a variety of electrical pulse formats to an anatomical site under a cast. The device described is a variation of the externally applied two electrode electrostimulator device to enhance tissue healing or bone growth and alternatively a cast embedded TENS device to mitigate muscle atrophy while encased in a cast.
U.S. Pat. No. 4,549,547 to Brighton et al., entitled “Implantable Bone Growth Stimulator,” issued Oct. 29, 1985, disclose a completely implanted bone growth stimulator with an external constant current source, and the device can be implanted and externally powered. U.S. Pat. No. 4,026,304 to Levy, entitled “Bone Generating Method and Device,” issued May 31, 1977, discloses a self-contained prosthetic which stimulates bone growth by a train of electrical pulses and a prosthetic system comprising a substrate material that can be electrically driven to induce tissue infiltration into the substrate pore structure. U.S. Pat. No. 6,937,905 to Carroll et al., entitled “Osteogenesis Stimulator with Digital Signal Processing,” issued Aug. 30, 2005, disclose a stimulator and a method for electrical stimulation of bone in which surface electrodes transmit an interferential current stimulation and a method for electrical stimulation of bone in which surface electrodes are positioned around an incision. The device described employs two cutaneous-surface mounted circuits controlled by a digital signal processor to produce and direct an interferential current that is nominally capable of somewhat precisely targeting of bone (or tissue) where osteogenesis is desired.
U.S. Patent Application 2004/0054379 to Carroll et al. entitled “Surface Electrical Stimulation for Increasing the quality and Quantity of Synovial Fluid in Joints,” discloses a device for improving synovial fluid by applying electrical stimulation in a sequencing pattern. U.S. Pat. No. 5,397,338 to Grey et al., entitled “Electrotherapy Device,” issued Mar. 14, 1995, disclose a flexible elastic sleeve including electrodes sewn into the sleeve that deliver electrical energy to tissues in and around joints. U.S. Pat. No. 4,313,438 to Greatbatch, entitled “Tissue Growth Control Apparatus and Method,” issued Feb. 2, 1982, discloses an electrode that is implanted and provides germicidal and healing treatment, with first a direct voltage applied of one polarity and thereafter of the opposite polarity. U.S. Pat. No. 4,846,181 to Miller, entitled “Soft Tissue Wound Healing Therapy Utilizing Pulsed Electrical Stimulation,” issued Jul. 11, 1989, discloses an active electrode positioned at a wound that provides pulsed electrical stimulation.
Those references disclose devices that employ some form of electrical stimulation to accelerate healing of both soft tissue and bone related trauma, and related infections. Most of these disclosures claims efficacious, cutaneous application of such electrical stimulation. Others disclose subcutaneous or implanted manifestations.
Cranio-facial bone repair and regeneration presents special challenges that relate to a variety of factors. Cranio-facial bone repair in the case of severe trauma, even using autologous material, is routinely complicated by lack of viable bone, short and long term disease process-related complications evident in existing tissue and bone, such as the degenerative condition of bone from long-term infection in sinus cavities, and post-operatively by factors such as the compromised vascular condition of the surgical site.
Low or largely non-existent levels of microcurrent at the site and in the immediate proximity of the wound affect the post-operative prognosis for cranio-facial bone repair and regeneration. In contrast to repairs to broken limbs where movement and stressing of the musculature and the limb itself routinely begin soon after the repair is affected, cranio-facial repairs exist in a state of relative stasis. In those cases where tissue has been compromised or replaced with other materials, such as frontal sinus obliteration where the sinus is filled with a compound such as hydoxyapatite, the prognosis for tissue and bone regeneration is problematic.
There is thus a present need for an apparatus that delivers pulsed or continuous micro-current stimulation to a site where tissue repair is desired, and which is implantable close to or at the wound. In particular, there is a need for an apparatus comprised of a harness of micro-scale electrodes attached to a power source and controller, and stabilized for placement on a substrate or patch made of a hypoallergenic, biodegradable material that is placed under the skin and absorbed by the patient as part of the treatment or healing process. There is particularly a present need for such a device with a primary application to cranial-facial conditions.